The present invention relates to optical disc playback apparatus and, more particularly, to optical disc playback apparatus which realize a scan search operation having a rate proportional to a playback rate of an arbitrary playback unit program, when playback unit programs are respectively played back with an optical disc which has multimedia data including digital moving picture data and digital audio data recorded thereon and which disc has playback data transfer bit rates varying with the playback unit programs.
In recent years, DVD (Digital Versatile Disc)-Videos which have greatly increased storage capacities are coming into wide use in place of conventional laser discs and video CDs, and many movies are put on the market. These DVD-Video standard discs are standardized attaching importance to playback of video without attaching importance to playback of various types of audio. Therefore, DVD-Video standard cannot realize playback in conditions of linear PCM, 192-KHz sampling frequency, 24 bit/sec, 2 channels, and more than 74 minutes, or playback in conditions of linear PCM, 96-KHz sampling frequency, 24 bit/sec, 6 channels, and more than 74 minutes.
Accordingly, DVD-Audio standard attaching importance to the playback of various types of audio is established as one of DVD standards. As shown in FIG. 9(a), the physical layer structure and file layer structure of DVD-Audio standard are the same as those of DVD-Video standard and only its application layer structure is different from that of DVD-Video standard. However, as shown in FIG. 9(b), DVD-Video standard and DVD-Audio standard have a common part in the application layer structure. FIG. 12 shows the comparison of contents between DVD-Video standard and DVD-Audio standard.
FIG. 10 shows a data structure of a file in the DVD-Audio standard disc having both of an Audio zone and a Video zone. The data structure according to DVD-Audio standard is divided broadly into a Volume zone and a File zone. Information of files in the File zone is recorded in the Volume zone. Video data files, audio data files, and files of data other than audio/video data (for example, computer data) are recorded in the File zone. The video data files, the audio data files, and the files of data other than audio/video data correspond to a DVD-Video zone, a DVD-Audio zone and a DVD-others zone, respectively.
In FIG. 10, four zones, i.e., a DVD-Volume zone 91, a DVD-Audio zone 92, a DVD-Video zone 93 and a DVD-Others zone 94 are defined. Among those, the DVD-Audio zone 92 comprises one piece of audio disc management information (i.e., Audio Manager, hereinafter referred to as xe2x80x9cAMGxe2x80x9d) 95 and one or more Audio Title Sets (hereinafter referred to as xe2x80x9cATSxe2x80x9d) 96. The DVD Video zone 93 comprises one piece of video disc management information (i.e., Video Manager, hereinafter referred to as xe2x80x9cVMGxe2x80x9d) 97 and one or more Video Title Sets (hereinafter referred to as xe2x80x9cVTSxe2x80x9d) 98. That is, according to DVD-Audio standard, one disc can simultaneously include the DVD-Audio zone 92 and the DVD-Video zone 93. When a title in the DVD-Audio zone 92 is to be selected, the ATS 96 is selected and when a title in the DVD-Video zone 93 is to be selected, the VTS 98 is selected. Although the DVD-Video zone 93 includes the VMG 97, when the whole disc is to be managed as a DVD-Audio standard disc, it is managed using the AMG 95 instead of the VMG 97.
ATS Information includes object position information indicating the position of audio data on the optical disc, sequence information indicating the playback order of the audio data, and object playback information indicating playback information of the audio data, as Program Chain Information (hereinafter referred to as xe2x80x9cPGCIxe2x80x9d). When playback is performed, a program which is specified by the PGCI is played back.
The DVD-Audio standard disc enables to play back various audio signals as shown by a diagram showing combinations of audio signals of a DVD-Audio standard disc of FIG. 13, for each program. It is possible that the number of channels, the sampling frequency and the number of quantization bits are defined for each of channel groups 1 and 2, and then combined. According to this combination, the data transfer bit rates are decided so as not to exceed the maximum data transfer bit rate (9.6 Mbit/sec).
In addition, according to a diagram of FIG. 14 for selecting conditions for each channel group of the DVD-Audio standard disc, the number of bits Q and the sampling frequency fs can be independently selected for each channel group in a range which does not exceed the maximum transfer rate (9.6 Mbit/sec). The minimum data transfer bit rate is obtained in a case where the number of channels=1, the sampling frequency=44.1 KHz and the number of quantization bits=16. The data transfer bit rate in this case is about 0.7 Mbit/sec. On the other hand, the maximum data transfer bit rate is obtained in a case where the number of channels=2, the sampling frequency=192 KHz and the number of quantization bits=24. The data transfer bit rate in this case is about 9.2 Mbit/sec. Therefore, the ratio of the minimum data transfer bit rate to the maximum data transfer bit rate is about 13 times.
There is a scan search operation of moving an optical pickup by a predetermined amount of address in a jumping operation while repeating the playback operation and the jumping operation, to search an arbitrary playback point.
In the case of DVD-Video standard disc, since video signals have compressed formats (MPEG), signals recorded on the disc have variable data transfer bit rates. Therefore, the relationship of the playback data amount to the time required for playback (hereinafter, referred to as playback time) is not uniform. Accordingly, in performing the scan search, when the jumping is performed by the predetermined amount of address, the playback time for each jumping is not fixed. As a result, even when a user executes the scan search operation to search an arbitrary playback point, the playback times do not vary in proportion to the time required for the scan search (hereinafter referred to as scan search time). Therefore, it is very hard to use the DVD-Video standard disc. Accordingly, in the case of DVD-Video standard disc, information of scan search addresses which realize the linear changes in plural playback times of a program at addresses which are previous and subsequent to the present address required for the scan search is recorded on the disc together with video signals. When the scan search is performed, the jumping operation can be performed on the basis of the scan search address information.
In the case of DVD-Audio standard disc, an audio signal necessitates a linear PCM format. Since signals recorded on the disc in the linear PCM format are not in compressed formats, the signals do not have variable data transfer bit rates but have a fixed data transfer bit rate. Therefore, the relationship of the playback data amount to the playback time is uniform. Accordingly, in performing the scan search, when the optical pickup is jumped by the predetermined amounts of address, the playback time for each jumping has a fixed value. Therefore, the scan search address information is not recorded on the DVD-Audio standard disc together with the playback signals, although this information is recorded on the DVD-Video standard disc together with the playback signals.
In the case of DVD-Audio standard disc, while the signals recorded on the disc have a fixed data transfer bit rate, the combinations of the number of channels, the sampling frequency and the number of quantization bits for each of the channel groups 1 and 2 as shown in FIG. 13 can vary by the playback program units. Accordingly, the data transfer bit rates vary by the playback program units. Therefore, in performing the scan search, when the optical pickup is jumped by the predetermined amounts of address, the playback time for each jumping is not fixed in different playback program units. As a result, even when the user executes the scan search operation to search an arbitrary playback point, the playback time for one scan search is not fixed in different playback program units. Therefore, it is very hard to use the DVD-Audio standard disc.
In addition, the program information (hereinafter referred to as xe2x80x9cATS#PGIxe2x80x9d) includes a program content (hereinafter referred to as xe2x80x9cATS#PG#CNTxe2x80x9d) indicating audio spec information, and thereby the combination of the number of channels, the sampling frequency and the number of quantization bits for each of the channel groups 1 and 2 can be previously known for each playback program unit. However, it is very difficult to univocally calculate the data transfer bit using the audio spec information, because there are combinations of the channel groups 1 and 2.
FIG. 11 shows the relationship between the playback time and the playback data amount for each playback program unit of the DVD-Audio standard disc. In the case shown in FIG. 11, when the data transfer bit rates of PG#1 to PG#4 are all equal (in this case, audio signals of PG#1 to PG#4 are all at 88.2 KHz, 20 bit/sec, 2 channels), the relationship between the playback time and the playback data amount is uniform as shown by line xe2x80x9cBxe2x80x9d. On the other hand, when the data transfer bit rates of PG#1 to PG#4 differ, the data transfer bit rate in each playback program unit is fixed, but the data transfer bit rate varies at each time when the different program unit is played, as shown by line xe2x80x9cAxe2x80x9d.
It is an object of the present invention to provide an optical disc playback apparatus which realizes the scan search operation in which the scan search time is proportional to the playback time.
Other objects and advantages of the present invention will become apparent from the detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the spirit and scope of the invention will be apparent to those of skill in the art from the detailed description.
According to a 1st aspect of the present invention, there is provided an apparatus for playing back an optical disc comprising an audio/video data storage area containing plural pieces of audio or video data which have playback data transfer bit rates varying with playback unit programs; and a title set management information storage area and a disc management information storage area as program management information storage areas containing program management information including title set management information and disc management information for playing back the plural pieces of audio or video data in the audio/video data storage area, respectively, and in a scan search for playing back necessary data in the audio or video data, the optical disc playback apparatus obtains last position data, initial position data, and a playback time of a program having the necessary data from the program management information, and decides an address amount of relative motion per one scan search operation for the program by arithmetic using the last position data, the initial position data, and the playback time.
According to a 2nd aspect of the present invention, in the optical disc playback apparatus of the 1st aspect, the program management information is read and stored in storage means at a time when the optical disc is mounted.
According to a 3rd aspect of the present invention, in the optical disc playback apparatus of the 1st or 2nd aspect, a value is obtained by the arithmetic, by subtracting the initial position data of the program from the last position data, and then dividing the subtraction result by the playback time.
According to a 4th aspect of the present invention, in the optical disc playback apparatus of one of the 1st to 3rd aspect, the arithmetic is performed by providing a comparison table having values of address amounts of relative motion for combinations of the last position data, the initial position data and the playback time of the program, and searching a value from the comparison table.
According to a 5th aspect of the present invention, there is provided an apparatus for playing back an optical disc comprising an audio/video data storage area which contains plural pieces of audio or video data; at least one title set management information storage area which contains audio or video sequence information constituting an audio or video sequence and indicating a predetermined playback order of the audio or video data, object position information indicating a position of the audio or video data on the optical disc, and object playback information of the audio or video data; and at least one disc management information storage area which contains title set position information indicating a position of the title set management information storage area on the optical disc, and disc management information for managing the whole disc, and the optical disc playback apparatus comprises reading means for reading the audio or video data, the audio or video sequence information, the object position information, the object playback information, the title set position information, and the disc management information from the optical disc, to play back the information; control means for controlling the reading means; disc management information storage means containing the disc management information which is obtained from the at least one disc management information storage area; and title set management information storage means containing the title set management information which is obtained from the title set management information storage area, and in the optical disc playback apparatus, the control means perform control to read the audio or video sequence information, the object position information, the object playback information, the title set position information, and the disc management information from the optical disc, thereby to store the information in the title set management information storage means or the disc management information storage means; control the reading means on the basis of respective contents of the disc management information, the audio or video sequence information, the object position information, the object playback information, and the title set position information; when performing a scan search operation, previously calculate an amount of playback data per unit playback time on the basis of the object position information and a playback time of each program included in the object playback information, and an amount of playback data which is obtained from a last position and an initial position of each program; and decide an address amount of relative motion per one scan search operation on the basis of the calculation result.
Therefore, the decided address amount of relative motion is used for each of programs in a range to be scan-searched, whereby the scan search operation in which the scan search time is proportional to the playback time can be realized.